Safety mechanism for presses



Dec. 29, 1942. H. K. LORENTZEN 2,306,785

SAFETY MECHANISM FOR PRESSES Filed June 1, 1940 e Sheets-Sheet 1 INVENTOR. Ham A. Z/ are/21 2612 RW,,W, m M;

I Am ATTORNEYS D .29, 9 H. K. LORENTZEN ,306,

SAFETY MECHANISM FOR PRESSES Filed June 1, 1940 6 Sheets-Sheet 2 llllllll lllllll INVENTOR.

Dec.29, 1942. I H K L R N EN 2,306,785

SAFETY MECHANiSM FOR PRESSES Filed June 1, 1940 6 Sheets-Sheet 3 s s s e iNVENTOR. Harv Kiowa/M1017:

MATTORNE S v Dec. 29, 1942. H. K. LORENTZEN 8 SAFETY MECHANISM FOR PRESSES Filed June 1/1940 6 Sheets-Sheet 4 Dec. 1 H. K. LORENTZEN "2,306,785

7 I SAFETY MECHANISM FOR PRESSES Filed June 1, 1940 v 6 Sheets-Sheet 5 4W ATTQRNE s 1942- I H. K. LORENTZEN 2,306,785

SAFETY MECHANISM FOR PRESSES Filed June 1, 1940 6 Sheets-Sheet 6 INVENTOR. Harv [if Larmizem W M M i XMATTORNEYS Patented Dec. 29, 1942 iJNi'iED s'rsrss smear OFFICE SAFETY MECHANISM FOR PRESSES Hans K. Lorentzen, Montclair, N. J. Application June 1, 1940, Serial No. 338,300

3 Claims.

This invention relates broadly to safety mechanism for protecting the operator of a press from injury due to his own carelessness or inadvertence. The invention is disclosed in the form of an attachment which may be applied to standard commercial punch presses; and the press itself will be described only to the extent necessary for a proper understanding of the safety mechanism.

The type of press illustrated is power-driven and is used to stamp metal parts. The power may be supplied to the press from any suitable source, such as a line shaft; and a foot treadle is used to trip the press and thereby initiate the stamping operation. Of course, tripping the press means that an operative driving connection is established between the press and the source of power. Presses such as referred to, are usually so constructed that they may be set for either semi-automatic or full automatic operation. In full automatic operation, the press continues to operate as long as the treadle is held depressed. In semi-automatic operation, the press stops after one complete cycle of operation; and the treadle must be released and again depressed to initiate the next cycle of operation, and so on.

The present invention provides safety mechanism which prevents the press from being tripped until the operators hands have been removed t from the vicinity of the punching members. Additionally the invention provides means for preventing the operator from surreptitiously setting the press for full automatic operation.

A general object of the present invention is i to provide safety mechanism which prevents operation of a punch press until after the oper ator has removed his hands from the vicinity of the punches.

Other objects are to provide such safety mechanism which mechanically accomplishes the desired result, which can be made as an attachment for standard punch presses, which is adjustable to operate with presses of different dimensions, which permits tilting of the body of the press to different working positions, which prevents surreptitious setting of the press for full automatic operation, which prevents operation of the press if the safety guard mechanism is removed, and which renders the treadle movement idle if a hand of the operator is in the danger zone of the punches.

Various other and detailed objects of the invention will be apparent to those skilled in the art from the present disclosure.

Fig. 1 of the drawings is a side elevation of a standard punch press with the present invention applied thereto. For the sake of clarity the press is shown with certain parts broken away.

Fig. 2 is an enlarged front view with certain parts broken away, showing the safety attachment on a press.

Fig. 3 is a horizontal section taken in general on the line 3-3 of Fig. 2.

Fig. 4 is an isometric view of the safety guard screen assembly.

Fig. 5 is an isometric view of one bracket of a pair of brackets used for supporting the guard screen assembly shown in Fig. 4.

Fig. 6 is an isometric view of the other bracket of the pair of brackets used for supporting the guard screen assembly, this bracket having a stud on which is pivotally mounted one of the link elements of the mechanism for operating the guard screen.

Fig. 7 is an isometric view of an operating link of the guard screen assembly, which link is assembled with the structure shown in Fig. 6.

Fig. 8 is a detail section taken approximately on the line 8-8 of Fig. 2.

Fig. 9 is a detail section taken in general on line 99 of Fig. 10.

Fig. 10 is a detail view, in front elevation, of a portion of the structure shown in Fig. 6.

Fig. 11 is a detail section taken in general on the line llll of Fig. 1.

Fig. 12 is a detail view, in side elevation, showing part of the press tripping mechanism.

Fig. 13 is a detail section, taken approximately on line Iii-l3 of Fig. 12.

Fig. 14 is an isometric view showing modifications which may be made in the mounting bracket shown in Fig. 6.

Fig. 15 is a detail elevational view showing the adjustment of operating links used in conjunction with the modified bracket shown in Fig. 14.

Fig. 16 is a detail section taken in general on line l6|6 of Fig. 15.

In the detailed description that follows, all elements designated by reference letters are parts of the standard punch press shown and hence are not per se part of the present invention. The elements designated by reference numerals are parts that have either been added to or substituted into the press, in accordance with the present invention.

The punching mechanism of the press is carried by frame A (Fig. 1), which is tiltably supported at B by a pedestal C. In the position shown in Fig. 1, the bed D of the press is horizontal, but for some types of work it is desirable to so tilt the frame A that the bed D will be inclined downwardly as viewed from in front of the press. The means for locking the frame A in difierent adjusted positions is not shown, since it is part of the standard punch press.

The frame A includes standards E and E (see also Figs. 2 and 3), which are provided with guideways for a reciprocating slide F to which a punch member is attached. Journaled in suitable bearings carried by standards E, E is a crank-shaft G from which the slide and punchcarrier F is reciprocated by a connecting rod H. Freely rotatable on crank-shaft G is a fly-wheel I which may be suitably driven, as by a belt. Clutch mechanism at J (Fig. 2) is operative, in response to downward movement of treadle K (Fig. 1), to establish driving connection between the fly-wheel I and the crank-shaft G.

In order to protect the operator from injury due to his own carelessness or inadvertence, I provide a safety attachment in the form of a guard screen assembly which encloses the zone of operation of the punch members of the press during the punching operation. This guard mechanism requires the operator to remove his hands from the zone of the punches before the press can be tripped.

Near the top of standard E there is affixed a horizontal bracket designated as a whole by H) (Figs. 2, 3, and especially This bracket has a mounting block II which is bolted directly to standard E. Slidably mounted on the block H is a horizontal arm [2 which makes rib-andgroove engagement with block H. The arm l2 has a longitudinal slot G3 which is pierced by a stud i4 threaded into block H at l5. Operating on stud I4 is a winged nut it which holds arm l2 in adjusted position. The outer end of arm I2 is provided with a vertical face l1 and a spring retracted pin l8 of the form shown. Bracket l0, and its component parts, constitute one of two supports on which a safety screen assembly is mounted. The screen assembly is positioned by the face H of the bracket and is secured by spring retracted pin l8, as will be described later. The other of the two supports for the screen assembly will now be described.

Near the top of standard E there is afhxed a horizontal bracket designated as a whole by 20 (Figs. 1, 2, 3, and especially 6). This bracket has a mounting block 21 which is bolted directly to the standard E. The outer end of the bracket is provided with a vertical face 11 and a spring retracted pin l8, which function as do face I! and pin 18 in mounting the guard screen assembly (to be referred to later). Journaled in bracket 23 are shafts 24 and 25 which are positioned at right angles to each other and which are operatively connected together by bevel gearing at 25. These shafts transmit motion to raise and lower the guard screen as the press is operated. Integral with bracket 20 is a chamber portion 21 which houses and supports a sliding pin 28 that is biased forwardly by a spring '3 29 (Fig. 9). This is a safety means which prevents operation of the press if the guard screen assembly is removed; and the manner in which it functions will be described later.

The guard screen assembly is best seen in Fig. 4. It comprises a rigid rectangular metal frame having upright members 30 and SI, and having top and bottom members 34 and 35. Included in the frame are channel members 35, 3i, and 38.

A vertically movable guard screen 39 slides in channels 36 and 31; and when the screen goes down, the lower edge portion thereof passes in front of frame bottom member 35 and into channel 38. Amxed to the bottom of the screen 39 is a rubber cushion which serves to soften the blow in case the screen descends on the fingers of the operator. Should this occur, however, full descent of the screen is prevented and the mechanism operates, as will be explained later, to prevent tripping of the press.

The guard screen assembly shown in Fig. 4 may be quickly mounted on and demounted from a press equipped with mounting brackets such as ShOWn in Figs. 5 and 6. To mount the guard screen assembly it is first held in a vertical position with 1% cars 4| and 42 against the bracket faces l1 and ll respectively and with the lower portions of keyhole slots 4! and 42' in alignment with the ends of pins l8 and I3 respectively. Pins l3 and 18' are then projected forwardly through slots 4i and 42' so that their heads will lie in front of cars 4| and 42, after which the guard screen assembly is moved downwardly to bring the upper portions of keyhole slots 4| and 42' in registration with the spring retracted pins l8 and 18' respectively. The springs retract the pins which withdraw the tapered heads of the pins a slight distance into the upper enlarged ends of slots 4| and 42', thereby holding the guard screen assembly in vertical position and preventing it from being accidentally moved in any edgewise direction.

Projecting rearwardly from the uprights 3G and 31 of the guard screen assembly are side guards designated as a whole by 44 and 45 respectively. These side guards are made of sheet metal and have at their forward edges channel formations which snugly and slidingly fit over uprights 3S and 3!, as is clearly seen in Figs. 4 and 11. Each side guard is provided with a hollow boss 43 which houses a spring retracted pin 46 that is adapted to enter any one of a series of holes 4'! in the uprights 3c and 3|. By pulling out knob 48, the spring retracted pin can be withdrawn from one of the holes 41 and the side guard shifted upwardly or downwardly to a new location where the pin 46 will enter another of the holes 41. This upward and downward adjustment of the side guards 44 provides for their appropriate location on different presses to prevent the operator from reaching around the guard screen to the zone of the punch members of the press.

Pivotally attached at 50 to the guard screen is a vertical operating link 5| through which motion is transmitted to raise and lower the screen in response to operation of the foot treadle K of the press. Pivoted at 53 to the top of link 5| is a second link 52 which is adapted to be connected in quick detachable fashion to receive motion from rock shaft 25 as will now be described.

Referring to Figs. 6, 10, 3, 9, and 2, there has already been described the rock shaft 25 which projects from the front of bracket 20. Pinned to this shaft near its forward end is an arm 54 having a projecting pin 55 and a lateral extension 56. Link 52 is provided with holes 52a and 52b (see Fig. 7) which are adapted to fit onto pin 55 and the end of shaft 25 respectively. Back of arm 54 there is pivoted on shaft 25 a U- shaped springy sheet metal clasp designated as a whole by 58. With the operating link 52 in po. sition on pin 55 and shaft end 25, clasp 58 may be swung from the position shown in Fig. 6 to the position shown in Fig. 2 by merely grasping the handle portion 58a of the clasp. When the clasp has reached the position shown in Fig. 2, further movement of the clasp with respect to arm 54 is arrested by a finger 581) that is integral with the clasp and strikes the top of arm 54. In this position a projection at 580 on the clasp snaps into hole 520 (see Fig. 7) on link 52, thereby preventing accidental movement of the clasp away from the position shown in Fig. 2. When the clasp is forcibly swung away from link 54, its movement is limited by engagement with stop pin 59 which projects from bracket 20.

It will be apparent that to attach gate operating link 52 to arm 54 it is merely necessary to open the clasp 58 to the position shown in Fig. 6 and then place the link 52 in position with the hole 52a embracing pin 55 and the hole 5% embracing the end of shaft 25. Then the clasp 53 is swung counterclockwise, locking the link 52 in attached position to arm 54.

As shaft 25 oscillates in response to operations of treadle K (as will be presently described), the movement is transmitted via links 52 and 5| to rais and lower the guard screen 39. Link 52 is provided with an L-shaped extension 5201 (see particularly Figs. 7 and 8) which, in the uppermost position of the guard screen, overlies pin 28 and prevents it from being moved outwardly by its spring 29. As arm 54 swings to lower the guard screen, the back face of arm 5:3 and then the back face of lateral extension 56 sweep over the end of pin 28, thereby keeping it in retracted position. If, however, the guard screen assembly is removed from the press, the detachment of link 52 removes L-shaped member 5201 from its association with arm 55; and when arm 54 rises, pin 28 is automatically projected beneath arm 54, as shown in Fig. 9. Since arm 54 is mechanically connected with the treadle K of the press (as will be described), the treadle cannot then be depressed to trip the press. In other words, re-

moval of the guard screen assembly autcmatically prevents operation of the press.

Referring to Figs. 1, 2, and 3, there is pivotally mounted on the frame of the press a rocker arm designated as a whole by L. The eccentric end of this rocker arm is bifurcated, as best seen in Fig. 3, thereby providing the arm with branches L and L". Swivelly mounted on branch L is a boss M. This boss is pierced by a rod N which has its lower end pivotally connected to treadle K; and a set screw makes holding engagement be tween boss M and rod N. In response to movement of treadle K the rocker arm L is rocked; and by means of the adjustment provided by set screw 0 the proper length of rod N can be included between rocker arm L and the treadle to effect the desired movement of rocker L with the body of the press tilted backwards to various degrees on the tilting mounting at B. Beneath rocker arm L there is an adjustable stop P which limits downward movement of treadle K. The branch L of rocker arm L is provided with a pivot pin Q (Fig. 2) on which is pivotally mounted a substantially vertical rod 13 which passes upwardly through a stationary member S that projects from the frame of the press. Above stationary member S the rod R is embraced by a helical spring T that is kept under compression by nuts at R which are threaded onto the end of rod R. It will be apparent that the spring T biases rod R in an upward direction. thereby biasing rocker arm L in a counterclockwise direction as viewed in Fig. l; and rocker L, acting through rod N, biases treadle K in an upward direction. In other words, when pressure is applied to treadle K it moves downwardly against the action of spring T, and when the treadle is released, the spring T restores the treadle to its uppermost position. As has previously been referred to, the conventional punch press includes clutch mechanism at J (Fig. 2) which is operative upon depression of treadle K to establish driving connection between the driven fly-wheel I and the crank-shaft G of 10 the press. This standard conventional clutch mechanism includes a pair of control slides V and V (see particularly Figs. 12 and 13). If one slide is pulled down (e. g. slide V), conventional clutch mechanism operates to put the press through one 15 cycle of the operation only, regardless of how long the slide is held down. If the other slide is pulled down (e. g. slide V) the press is put through repeated cycles of operation which are not terminated until the slide is released. Springs 22 and o bias control slides V and V respectively in an upward direction; and these slides are provided with pins Va and Vb which project through slots in the frame to receive an operating link for pulling down the control slides V and V 25 respectively.

Shown in full lines there is an operating link 60 which is pivotally connected to pin Va and which extends downwardly to pin 6| which is common to links 60, 62, and 63. Link 62 has its lower end positioned between the two arms of bifurcated rocker arm L, and it is pivotally connected at this point to rocker arm L. Thus when treadle K is depressed and rocker arm L moved clockwise (Fig. 1), link 63 is pulled in a generally 5 downward direction which in turn moves downwardly first pin El and then link 65 The downward movement of link 69 draws downwardly control pin Va, which correspondingly moves control slide V to initiate a cycle of operation of the press. When the treadle is released, it is restored by spring T; and control slide V is similarly restored by spring 0. By manually removing link 60 from pin Va and connecting it to pin Vb, control slide V is similarly pulled down upon depression of treadle K, resulting in continuous operation of the press as long as treadle K is held depressed.

Link 63 is pivotally mounted on a fixed stud 64 which projects from the frame of the press. Thus, when common pivot Bl is moved downwardly in response to depression of treadle K, the

link 63 is swung in a clockwise direction (Fig. 1).

Pinned to the end of shaft 24 is a rocker arm 65 which makes pin and slot connection at 6? with 65 that end of link 63 which is nearest the front of the press. Thus, when link 553 is swung in a *clockwise direction to the dotted line position shown in Fig. 1, shaft 24 is moved counterclockwise; and there has already been described mechanism by which such motion of shaft 2 3 causes the lowering of safety guard screen 39. When treadle K is released and link 63 isrestored in a counterclockwise direction to the position shown in full lin s in Fig. 1, shaft 2 3 65 is moved in the reverse direction, thereby raising the guard screen 39.

As shown in Fig. 1, the link 69 makes slot connection with the common pivot 6!. Thus, upon the initial downward movement of common pivot 70 6| in response to depression of treadle K, the link 60 is not moved, though motion is immediately imparted to link 63 to lower the guard screen 39. The parts are so proportioned that operating movement of link 65 does not occur unt l the guard screen has been lowered sufiiciently to place its lower edge below the upper edge of member 35 of the guard screen assembly. Thus, if an operators hands or fingers prevent this degree of descent of the guard screen 39, motion of the foot treadle and associated parts are arrested, with the result that operating movement is not imparted to link 68 to trip the press. If, however, nothing blocks movement of the guard screen, the motion continues with the lower edge of the guard screen moving downwardly into channel 58; and along with this additional movement, link 60 is pulled downwardly and trips the press. It will be apparent that this adequately protects the operator against his own carelessness or inadvertence as the press cannot be tripped until his hands or fingers have been removed from-the zone of the punching members.

To shift control links 68 from pin V0. to pin Vb and thereby set the press for full automatic operation instead of semi-automatic operation,

it is necessary to manually pull the link 60 off the end of pin Va. The frame is provided with ears l and 'H through which pass a headed pin 12 that lies adjacent to link 68 and prevents its removal from pin Va until pin 12 has been withdrawn from the ears l8 and I I. Passing through the small end of pin H is a pad-lock 14, the key to which is retained by the shop superintendent. Thus the operator is prevented from removing pin 12 and setting the press for full automatic operation without proper authorization.

Assuming that look pin 12 has been removed, the procedure for shifting control link 68 to pin Vb involves the manipulation of parts which will now be described.

Attached to the side of the press frame there is a vertical hand lever 15 which is adapted to be rocked in a plane perpendicular to the paper in Fig. 1. The lower portion of this lever is offset outwardly from the press, as shown inFig. 2. .1

Just above the offset this hand lever bears against a fulcrum and spacing member 16 which is against the side of the press; and at this point the hand lever is pierced by a loose fitting bolt 11 screwed into the frame of the press. This permits the lower end of hand lever 15 to be forcibly moved directly toward the frame of the press with rocking movement of the lever (in a plane perpendicular to the paper in Fig. 1) which throws the upper end of the lever 15 away from the frame of the press. The upper end of the hand lever is bifurcated and straddles pin 84 immediately behind link 63, as shown in Figs. 1 and 3. This rocking movement of the hand lever forces link 63 outwardly against the action of spring 64a. This moves common pivot pin Bl outwardly and permits link 68 to be withdrawn over the end of control pin Va, whereupon it can be swung edgewise and placed in position on control pin Vb. Release of the hand lever 15, of course, restores that lever and link 83 to the position shown in Fig. 3.

The mounting bracket i8 (Figs. 3 and 5), which supports the left side of the guard screen assembly, is adjustable to position the guard screen different distances from the press standard E. This adapts the bracket for use on presses of different sizes and proportions. The right hand bracket 28 (Figs. 3 and 6)' is shown as non-adjustable; and it it be so made, difierent brackets would have to be used to correspond with the different adjustments given to bracket l0. However, Fig. 14 shows adjustments which may be incorporated into bracket 2!] so that it can be adjusted correspondingly to bracket (0.

In Fig. 14 a housing member 80 has associated with it through the means for supporting the right hand side of the guard screen assembly, and also the bracket-supported part of the mechanism for raising and lowering the guard screen. As in Figs. 6 and 10, there are the vertical face l1 which positions the guard screen assembly, and the spring retracted pin l8 which secures the guard screen assembly. Likewise, there are shafts 24 and which are geared together and transmit motion to raise and lower the guard screen. Housing member 88 makes rib-and-groove engagement with intermediate member 8| to which it can be locked in various adjusted positions by cap screw 82. Thus this adjustment provides for the face l1 being positioned at different distances from the press standard E (Figs. 2 and 3) to which the bracket is adapted to be bolted by bolts passing through mounting block 84. The intermediate member 82 makes rib-and-groove engagement with the mounting block 84 and it can be locked in various laterally adjusted positions by cap screw 86. This adjustment provides for mounting guard screen assemblies of different widths, or for mounting a given width assembly on presses having the standards E and E different distances apart. It will be understood that Fig. 14 shows modifications to be incorporated into bracket 20 (Figs. 3 and 6) and therefore duplication of such things as the safety pin 28, arm 54, and clasp 58 from Fig. 6 has been avoided.

When housing 88 is shifted inwardly or outwardly, an arm 68 (Fig. 1) of different length and a link 83 of different length may be substituted to make operating connection to pivot pin 6|. However, arm and link 63 may be adjustably connected as shown in Figs. 15 and 16. For this purpose the arm, now designated as 68, is provided with a pivot pin 87 which can be fixed at any position along a slot 88 provided in the arm. Pin 81 then pivotally pierces the slot 89 in link 83, which slot is long enough to properly cooperate with pin 81 in any of its positions along slot 88.

In compliance with the patent statutes, I have disclosed the best form in which I have contemplated applying my invention. It will be realized, however, that various modifications are possible within the scope of the invention.

I claim:

1. Safety mechanism for punch presses having control means to initiate a cycle of press operation, said mechanism comprising: a guard screen shiftable from open position to guard position; mechanism coordinated with the control means of the press to shift the guard screen to guard position before actuation of the press is initiated, said mechanism including a member to transmit motion to the guard screen and a detachable operating connection from said member to the screen; and means automatically operative upon detachment of said connection to block the movement of said member and thereby prevent actuation of the press.

2. Safety mechanism for punch presses having control means to initiate a cycle of press operation, said mechanism comprising: a guard screen shiftable from open position to guard position; mechanism coordinated with the control means of the press to shift the guard screen to guard position before actuation of the press is initiated, said mechanism including a rock shaft and an arm rocked thereby and also a quickdetachable operating connection from said arm to the screen; a blocking pin biased to move into blocking position relative to said arm when the arm is in non-operated position; means associated with the arm to hold the pin against blocking movement when the arm is in operated position; and means carried by said detachable connection to hold the pin against blocking movement when the arm is in non-operated position and the connection is attached to the arm, whereby the pin moves into blocking position when said connection is detached from the arm.

3. Safety mechanism for punch presses having control means to initiate a cycle of press operation, said mechanism comprising: a guard screen shiftable from open position to guard position; mechanism coordinated with the control means of the press to shift the guard screen to guard position before actuation of the press is initiated, said mechanism including a rock shaft and an arm rocked thereby and also a detachable operatirig connection from said arm to the screen; blocking means biased to move into blocking position relative to said arm when the arm is in non-operated position; means associated with the arm to hold the blocking means against blocking movement when the arm is in operated position; and means carried by said detachable connection to hold the blocking means against blocking movement when the arm is in nonoperated position and the connection is attached to the arm, whereby the blocking means moves into blocking position when said connection is detached from the arm.

HANS K. LORENTZEN. 

